I built a rocker concave rocker table with the following items, please excuse my descriptions, I never remember the proper names for things

2 sheets of 1/4" board that have holes drilled in them 1" apart. That is, they're covered in these 1/4 holes design for hooking your tools on to in your workshop

A few yards of 1/4" round wooden pole.. stick.. whatever

a sheet of 1/4 or 1/8" board flexible enough so that you can arc it (you'll know what I mean later)

So, lay down the first two boards and fix them together so that you have a 1/2" sheet. Cut up the wood pole in to 2" sections and insert along the long edge of the 1/2" sheet. Cut up the flexible board (from the short side in to 4 or 5" wide strips.

Then start trying to put the flexible board strips inbetween the pegs on your main board and cut down until you get your desired concave. I make the flexible boards shorter in the middle and longe at the ends to give rocker.

I weigh down my kiteboard with weights on two strips of the flexible board running along the edges of the kiteboard.

Its all VERY non scientific but super cheap and quick to build. I've put amazing concave in my boards (2x 1/4" divinycell)

Let me know if any part of that is not clear and I'll explain further.

Chassan, imagine a set of ribs (as in your rib cage) laid down on the table.

Lets say theres four ribs for simplicity. 1-2-3-4. Ribs 1 & 4 are for the tip and tail of my board, 2 & 3 in the center.

In my rocker table, which is completely flat, I place pegs for either end of rib 1 where my board tail is going. I cut out rib 1 from flexible wood just so that its longer than the space between the pegs and then flex it and place between the pegs. Now you have a raised arc. I cut it down in 2mil bits to get the desired concave

Rib 4 will be the same length and the pegs the same distance apart for the other end of the board.

To get the same concave in the center of the more, the ribs will be shorter and the pegs closer together. I just cut down rib 2 until I get the desired rocker. rib 2 will be lower that ribs 1 & 4. Make rib 3 = 2.

so the side view of the table looks like this
1234
_ _ ribs 1&4
_ _ ribs 2&3
------ Table pegs

and the plan of the table looks like this
1234
_ _
__
__
_ _

The difference between the pegs at the center of the board and the ends on a 4' board is about 1.5"

if you still need pictures I can take some, but it will take some time to organise.
[/img]

It takes me about an hour to fully shape a non-directional,I take a full depth 1/4 inch with the hand planer down the middle of the bottom and leave a 2 inch untouched edge along rails and plane and sand to finish .My usual board has a thickness of about 1/2 in in the middle out to whatever I want for rails ,I use 3/4 inch pvc foam ,I cannot imagine an easier way, but it would be hard to get it exactly the same as before ,If I was to produce this over and over I would just have the boys C.N.C. it for me for $20